Question: $ A = \left[\begin{array}{rrr}2 & 0 & 1 \\ 1 & 2 & 2 \\ 2 & 1 & 2\end{array}\right]$ What is $ A^{-1}$ ?
Answer: $ = \left[\begin{array}{rrr}2 & 1 & -2 \\ 2 & 2 & -3 \\ -3 & -2 & 4\end{array}\right]$